Cornflower, also known as bachelor’s button, is an annual wildflower from the Mediterranean region that now grows wild across much of North America. Its bright blue flower heads show up along roads, in fields and ditches and on other disturbed open ground, and the plants keep blooming from late spring well into fall.
What looks like a single flower is really a head of many small florets. The ones around the edge are enlarged, ragged and sterile, which gives the head its frilly outline, while the smaller florets in the middle produce the seeds. Blue is the usual color, but white, pink and purple plants turn up as well. Bees, flies, beetles and wasps all visit the flowers. The slender stems and narrow leaves are covered in a loose, grayish wool.
Cornflower is not native to Oregon, but it is not on the state’s noxious weed list either. Several of its close relatives in the genus Centaurea, including spotted, diffuse and meadow knapweed, are listed noxious weeds, so any similar plant with pink or purple flowers deserves a second look. Around Mt. Hood, cornflower is a plant of low elevations and disturbed ground.
How to identify it
An annual 8 inches to about 3 feet tall with slender, branching, grayish woolly stems and narrow, mostly untoothed leaves up to 5 inches long. Each branch ends in one flower head, usually bright blue, with enlarged, ragged outer florets. The green bracts beneath the head have narrow, dark, fringed edges near their tips.
Look-alikes
Spotted knapweed, a listed noxious weed in Oregon, is a short-lived perennial with purple or sometimes cream flower heads and black-tipped bracts. Cornflower is an annual whose flower heads are usually bright blue with large, ragged outer florets.
Habitat
Roadsides, fields, ditches, meadows and other disturbed open ground at low elevations.
Sightings in the forest
412 research-grade sightings in Mt. Hood National Forest on iNaturalist, most recently on October 8, 2026. See them on iNaturalist →